eighth - that is, Noah, and seven others. Contrasted with the densely peopled “world of the ungodly.”
preacher - not only “righteous” himself (compare 2Pe 2:8), but also “a preacher of righteousness”: adduced by Peter against the licentiousness of the false teachers (2Pe 2:2) who have no prospect before them but destruction, even as it overtook the ungodly world in Noah’s days.